How can DNA be found in extinct animals?

Answer 1

There are a number of conditions that must apply. Notable are suitable preservation environment, and stability.

If the animal has been preserved in ice and stayed frozen until now such as some cases of the Woolly Mammoth, they have the best chances. Their DNA is relatively easy to extract, although it had major problems with contamination from modern and ancient bacteria. This bacterial DNA massively outweighed the Mammoths' DNA, requiring massive use of computers to search the DNA as it was sequenced comparing it to known bacterial samples vs. Elephant DNA.

There are examples where extinct animal DNA has been found where it is a relatively bad environment, but a stably bad environment. For instance giant ground sloth bones were found in caves in deserts that were technically too hot for good preservation, but because the caves had little change in temperature or humidity there was still DNA to extract.

It is extremely rare to find DNA in fossilized animals. However, in a case discovered in the US, a 67 million year old Tyrannosaurus Rex was found with viable protein which could be use for comparing relation of species, but never cloning. The paleontologists found the preserved tissue inside bones fossilized with large amounts of iron and managed to extract small traces of protein. In this case the large amount of iron worked out as a preservative.

Often only Mitochondrial DNA is preserved. This is because most cells have several, or in some cases many mitochondria, and mitochondria additionally have an extra layer of protection. Mitochondrial DNA has been extracted from a very large number of relatively recently extinct animals that were poorly preserved.

Because the amounts of preserved ancient DNA in fossils is so tiny, very careful steps must be taken. Touching the remains bare handed, or even in some cases breathing on them can produce such massive contamination that the ancient DNA is a drop in the ocean. The remains, or more usually pieces of remains, are very carefully cleaned to try to remove as much outside contamination as possible. Samples are taken and put into a PCR (Polymerase Chain Reactioin), which causes the DNA to reproduce itself again and again and again, as much as possible.

Once results start to come in, it's off to the computers. Since the vast majority of DNA is contamination, specifically bacteria, computers are used to identify the chunks of bacterial DNA and mark them for exclusion as fast as possible. Once this gives an idea of what kind of original DNA is in the sample, it's possible to modify the PCR process to target the original DNA and ignore the contaminant DNA.

This is done until there are enough pieces read in to start assembling them, often by matching them to what's thought to be the closest living relative.

Answer 2

DNA can be found in extinct animals by extracting it from well-preserved remains such as bones, teeth, or hair. Samples are collected and analyzed for genetic material, allowing scientists to study the genetic information of these animals and even potentially recreate it through cloning techniques.